1. Field of the Invention
The present invention relates to an eye direction detecting apparatus. More particularly, the present invention relates to an eye direction detecting apparatus suitable for use in a camera having an automatic focusing device in which focusing zones of an auto focus optical system, each of which focusing zones corresponds to each of various focusing zones of the finder, are located in optically generally conjugate positions with a plurality of focusing zones disposed within a view field of the finder, and focusing is made on an object which is visually overlapped with a focusing zone corresponding to a selected one of the various focusing zones of the finder.
2. Description of Related Art
An auto optical focus detecting device for a camera having an auto focus optical system has heretofore been developed. FIG. 1 is a schematic view Showing an optical system of an auto optical focus detecting device of, a single-lens reflex camera, for example, which has an auto focus optical system. In the figure, 1 denotes a photographic lens, 2 a subject to be photographed, 3 a view field mask, 4 a condenser lens, 5 a diaphragm mask, 6 and 7 a separator lens serving as an image splitting optical element for reimaging, and 8 a CCD serving as an image receiving element. The view field mask 3, the condenser lens 4, the diaphragm mask 5, the separator lenses 6 and 7, and the CCD 8 are integrally modulated as one unit and constitute an auto focus optical system 9.
In this auto focus optical system 9, the view field mask 3 is disposed in the vicinity of a film equivalent plane 10. The film equivalent plane 10 is in a position optically conjugate with the subject 2 to be photographed through the photographic lens 1. A well focused image 11 of the subject 2 is formed on the film equivalent plane 10 when the photographic lens 1 is in focus. The condenser lens 4 and the diaphragm mask 5 have the function of splitting the photographic light passing on both right and left sides of the photographic lens 1. The separator lenses 6 and 7 are in a position optically conjugate with the photographic lens 1 through a condenser lens 4.
The separator lenses 6 and 7, as shown in FIG. 2, are disposed in the horizontal direction. Further, the separator lenses 6 and 7 face imaginary opening areas 14 and 15 of an exit pupil 13 of the photographic lens 1 through a zone 12 located in a position optically conjugate with a center zone of a finder as will be described. The separator lenses 6 and 7 intake a bundle of light rays passed through the opening areas 14 and 15. The image 11 formed on the film equivalent plane 10 is reimaged as images 11' in two areas on the CCD 8.
Distance between the images 11' well focused (see FIG. 3(a)) is represented by l.sub.o as shown in FIG. 4. When the photographic lens 1 is focused in a position in front of the focal point of the aforementioned well focused image as shown in FIG. 3(b), the distance between the images 11' becomes less and, as a result, the distance between signals S corresponding thereto becomes less than the distance l.sub.o. On the other hand, when the photographic lens 1 is focused in a position behind the focal point of the aforementioned well focused image as shown in FIG. 3(c), the distance between the images 11' becomes greater and, as a result, a distance between signals S corresponding thereto become greater than the distance l.sub.o. Since the distance between the images 11' is changed in proportion to a defocusing amount of the photographic lens 1, in the conventional auto optical focus detecting device of a single-lens reflex camera, a distance between images of the CCD 8 is detected and the signals are arithmetically processed, and the photographic lens 1 is moved to the focal position with reference to the focusing direction and defocusing amount of the photographic lens 1. And, as shown for example in FIG. 5, if the optical focus is found by framing such that desired subject 2 to be photographed is located in the center zone 17 arranged at the center of the finder 16, the photographic lens 1 is automatically brought into a focusing state. If a photograph is taken in the foregoing state, a well focused photograph can be obtained.
In this conventional auto optical focus detecting device of a single-lens reflex camera, since the zone is located in the center of the finder 16, a desired subject 2 will be positioned in the center of an obtained photograph unless an adequate alternate arrangement is made. There are some instance, it should be noted, where a desired subject 2 is preferably positioned in a peripheral area of a photograph instead of the center of the photograph. To this end, therefore, in the conventional single-lens reflex camera, a focus lock mechanism is provided. That is, the subject 2 to be photographed is positioned in the center of the finder 16 to automatically find the distance to the subject 2. In that state, the focus is locked. If a photograph is taken in the framing as shown in FIG. 6, a photograph can be obtained in which a desired subject 2 is positioned in the peripheral area.
However, in this conventional auto optical focus detecting device of a single-lens reflex camera, the subject 2 must first be positioned in the center of the finder 16. Then, the photographic lens 1 must be moved to a focusing state. In that state, the focus must be locked to fix the photographic lens 1. Then, the framing must be performed once again. Only thereafter can a photograph be taken. Therefore, much time and labor are required before the camera is ready to take a photograph.